The invention relates to heat exchangers for mixtures of air and solid particles, particularly for woodworking shops, paint shops, poultry farms and industrial environments of the like.
The rate of heat transmission in an air-to-air heat exchanger is generally higher for air flowing in a turbulent motion than for air flowing in laminar or streamline motion. The type of air flow inside a tube is defined mainly by the velocity of the air, the size and length of tubes and by the presence of deflectors inside the tube.
The rate of heat transmission in a heat exchanger is also depending upon the coefficient of heat transfer through the wall of the tubes. The heat transfer capacity of dust being much less than for metal, any thickness of dirt deposit inside the tubes does adversely affect the efficiency of the exchanger.
A common fact with industrial air-to-air heat exchanger is that the inside surface of the tubes requires frequent cleaning to maintain an acceptable efficiency. Hence, without a stringent maintenance program, the economic viability of the unit is often unsure.
A common fact with industrial heat exchangers is that replaceable filters are installed at the inlet end of the exchanger to filter dust particles from the incoming air. The inconvenience of filters is that the amount of dust particles collected reduce the air flow proportionally.
Another common fact with industrial heat exchangers is that, despite the use of filters, deflectors to increase turbulence inside the tubes are not used, because of a possible accumulation of dirt on the deflectors, and a resulting premature loss of efficiency.
Therefore, the high cost of maintenance, the reduced air flow periods between filter changes, and the absence of deflectors inside the tubes are the main causes for poor economic and physical performance of industrial air-to-air heat exchangers.